Ultimate Disposal of Wastes by Pyrolysis and Incineration

C. A. HESCHELES, P. E. and R. F. BONNER, JR.

Malcolm Pirnie. Inc ••

Consulting Environmental Engineers.

White Plains. N.Y •

•

ABSTRACT

This paper describes a new disposal facility designed to reduce thermally, without causing pollution, liqUid/fluid industrial wastes received from process industries and skimmings from wastewater treatment plants in the Greater Cincinnati, Ohio area.

The Metropolitan Sewer District of Greater Cincinnati, Ohio (MSD), has authorized the design and construction of a facility to reduce liquid/fluid industrial wastes by pyrolysis and incineration. The facility will be constructed at the site of the existing Mill Creek Wastewater Treat­ment Plant. I t is believed that this is the first venture in the United States by a municipal authority to provide contractual disposal for wastes otherwise prohibited by ordinance from municipal sewers.

The design provides for the District to receive liquid/ fluid industrial wastes of varying calorific value by tank truck. The various wastes, when received, are pumped to storage tanks, then blended to produce a liquid with a calorific value capable of sustaining combustion without the use of supplementary fueL Certain liquid/fluid and solid residues from the wastewater treatment plants will also be incinerated in the system.

NEEDS AND STUDIES

When an existing dump for industrial wastes was closed by the Ohio State Board of Health, industries within the

321

boundaries of the MSD (Le., .the City of Cincinnati and Hamil ton County , Ohio) discharging liquid/ fluid wastes not amenable to conventional wastewater treatment were required to find another method of disposaL

In conjunction with industry and the Cincinnati Cham­ber of Commerce, the MSD offered to investiga te altern­ative methods of disposal and, if a feasible method were found, to design and construct a facility that would pro­vide for ultimate disposal of these unusual wastes.

Investigations were made of available combustion sys­tems such as fluidized bed, cyclone furnace, rotary kiln, etc., for thermal reduction of industrial wastes prior to the final selection of a safe opera tional design.

The fluidized bed furnace operates with a positive pres­sure and is subject to causing a hazardous operating condi­tion if a leakage occurs anywhere in the system. The in­vestigation showed that the fluidized bed combustion system was not desirable for thermal reduction of the industrial wastes generated by industries within the MSD.

The operating temperatures of a thermal reduction furnace are higher than the normal temperatures encoun­tered in a fluidized bed furnace. The thermal reduction furnace operates with a negative pressure to prevent the escape of noxious gases to the atmosphere.

As a result of these investigations conducted prior to selection of the system, a report was submitted to MSD, with recommendations for the construction of a thermal reduction facility incorporating the features described herein.

FACILITY DESCRIPTION

The facility to be constructed on the site of the Mill Creek Wastewater Treatment Plant includes a materials handling and storage area, a Control Building, Laboratory

•

and Utility Building, and a 1 50 million Btu per hr ther-mal reduction unit. It is anticipated that the liquid/fluid industrial waste thermal reduction facility will be opera­tional by late 1 975.

The thermal reduction unit includes a rotary kiln, cyclone furnace, combustion chamber, high-energy ven­turi scrubber, induced draft fan, and a stack. Flue gases from the kiln and cyclone furnace flow into the common combustion chamber. The flue gases from the combustion chamber enter the venturi scrubber and then discharge through an induced draft fan into the stack to atmosphere. The system incorporates the latest available designs in combustion, combustion control, and air pollution con­trol.

Ash from the combustion chamber and the rotary kiln, together with fly ash from the scrubber, will be discharged hydraulically to an ash disposal lagoon on the treatment plant site.

The materials handling and storage area includes pumps, meters, storage tanks for processing liquid/fluid

wastes, conveyors, and a shredder for processing solid wastes. See Fig. 1 - Plan and Fig. 2 - Diagram.

WASTE TYPES AND

CATEGORY CHARACTERISTICS

To obtain data as current and as complete as possible on , existing wastes, a "liquid waste" questionnaire was mailed to industrial concerns located...within the Metropolitan Sewer District. In addition to the questionnaires, personal interviews were conducted to amplify and clarify the re­sults of the questionnaire.

The major common characteristic of the wastes from the industries is the combustibility of the material. Some wastes are dry, i.e., completely nonaqueous; and others contain water in amounts ranging from a few percent to 94 percent, for example, an unconcentrated soluble cut­ting oil waste.

The various wastes are grouped into seven general cate­gories as listed in Table 1 .

The allocation of wastes to the various categories was based on consideration of the problems concerned with storage and blending of compatible wastes to facilitate combustion. Brief descriptions of the categories follows:

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Table 1 Classification of Liquid Fluid Wastes

General Description

Light hydrocarbons & non· aqueous solvents

Medium to heavy-weight hydrocarbons etc.

Low water content aqueous wastes

Dirty solvents

High water content aqueous wastes, semi-sol ids and sludges & low heating value liquids

Skimmings from Mill Creek WTP

Spent earth

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Materials Included

Benzol, tol uol, aromatics cellQsolve

Crankcase oils, still bottoms, transformer oils

Clabberstock, soaps, fatty acids, alcohols, cutting oils

Kerosene, soluble oil residue, oil soluble inks, ink wastes, organic pigments

Paint overspray liquid polymers, chlorinated solvents, oil sludge

Grease, soaps, etc.

Diatomaceous earth, oils

Class I: Light Hydrocarbons and nonaqueous solvents.

These materials include low flash point wastes and such items as paint thinners, aromatics (benzene, toluene, xylol) etc. This type of waste can serve two useful func­tions in waste blending: a) at start-up to assist fuel oil in the initial heating prior to firing the heavy blends that comprise the principal burning load ; b) to reduce the viscosity of heavy wastes below 200 SSU (Say bold Seconds Universal).

Class II: Medium-to-heavyweight hydrocarbons and

similar waste materials. This type of waste includes such materials as waste crank case oils, still-bottom residues, and discarded transformer oils. These materials all have high flash points but relatively low ignition temperatures. Generally, the moisture content is well under 10 percent. In a hot furnace, with an excess of 30 to 50 percent air, these substances will burn readily and produce less than 3 percent ash of low sodium content. These wastes will require insulated storage tanks and auxiliary heat to main­tain proper fluidity for handling during cold weather.

Class III: Low water content aqueous wastes. Included in this category are sludges from fatty acid and glycerine production, c1abberstock (a mixture of approximately 70 percent biodegradable oil and 30 percent water), starches, reject fatty acids, and waste soluble oils. These wastes may be blended in limited proportions with the heavier substances in Class II but will need to be stored in in­sulated and heated tanks to prevent congealing and freez­ing of the water content during winter weather.

Class I V: Dirty solvents. This group includes kerosene, soluble inks, oil-solvent residues, etc. Storage tanks for this group do not require insulation or heating. Ash con­tent after burning may vary from 4 to 10 percent of the original weight.

Class V: High water content aqueous wastes. Included in this group are aqueous mixtures of paint, enamel, and lacquer oversprays, liquid polymers in water, paint sludges, and possibly some chlorinated hydrocarbons.

Class VI: Skimmings from wastewater treatment

plants. This category is not an industrial waste per se; it is a product of municipal wastewater treatment plant. It consists of flotable material skimmed from the primary and secondary clarifiers. As removed from the clarifiers it contains a high water content, which may be reduced to about 60 percent by subcanting after quiescent storage.

Heating to a temperature of 160°F makes it possible to reduce the moisture content to approximately 50 per­cent. The grease fraction of the skimmings has a high heat value which makes its disposal by burning attractive':

Class VII: Spent earth. High water content waste -contains 70% water, 13% oil, and 17% dia tomaceous earth.

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TRANSPORTATION

The MSD is not organized to provide carting service for the industries. Therefore, all liquid/fluid wastes will be transported from place of origin to the Mill Creek Plant site by the companies or industries concerned. There are also private haulage companies in the District area that can transport the wastes from individual plants to the treat­ment site.

Whether the industries provide their own transporta­tion service, use an independent haulage service, or band together to provide a haulage service is not for the MSD to decide. On the other hand, if the MSD facilities are to operate efficiently, modern and standardized methods of delivery and receiving must be developed.

RECEIVING O F WASTES

All liquid industrial wastes will be metered, inspected, analyzed, and pumped to their respective storage tanks. Questionable wastes will be pumped to standby receiving storage for further investigation prior to final storage.

Large-quantity wastes will be delivered in tank trucks equipped with transfer pumping facilities to pump the waste from the tank truck directly to the storage tank. Pumps have been provided at the loading dock for trucks not so equipped.

Small-quantity wastes, especially viscous wastes, will be delivered in unitized containers such as Dempster-Dump­ster units or in 55-gal disposable drums.

Facilities for transferring these wastes to the plant storage tanks have been provided at the loading dock.

Wastewater treatment plant wastes such as skimmings, screenings and grit will be delivered directly to the facility by local plant transportation. The skimmings may be pumped or trucked depending on the original location of the wastes.

MATERIAL HANDLING AND STORAGE

All wastes will be received at the Control Building. The type of waste, quantity, and container will be checked by the plant operator before unloading of the waste is per­mitted.

FLOW METERING

An automated system will allow the operator to select the proper storage tanks for the waste. This system can handle four tank trucks, each containing a different waste, simul taneously.

Flow meters will be installed on each of the liquid waste lines with resettable registers and a ticke t printer.

A card-reader/valve-selector station will allow the operator to select the proper valve, indentify the card holder and activate the system. A logic cabinet will contain the neces­sary logic required to decode the card, and check its validity.

STORAGE TANKS

The storage tank area will include tanks designated to store wastes that have been analyzed and are ready for thermal reduction. Storage is classified into the following categories:

Light hydrocarbons Medium to heavy hydrocarbons Low aqueous hydrocarbons High aqueous hydrocarbons Dirty solvents

LIQUID WASTE STORAGE

Spent earth Skimmings Fuel oil Caustic Wastes Alkali

The storage area of liquid waste will include: tempor­ary holding tanks, batching tanks, main storage tanks, and transfer pumps.

The unloading dock, will have four holding tanks for the operator to store questionable wastes until a deter­mination as to final disposition is made.

Batching tanks include four tanks used to prepare an B·hr shift waste feed for the rotary kiln and the cyclone furnace. One set of tanks will be filled while the other set is feeding the furnaces.

An individual ultrasonic level-monitor system will con­trol the level in each storage tank. Two high-level alarms and one low-level alarm will warn the operator of unde­sirable conditions.

MAIN CONTROL PANEL

A graphically illustrated panel will provide indication and control for the entire material handling operation. The operator may control, and see at a glance:

Position of tank discharge valves Start and stop pump motors High and low level alarm in storage tanks Start and stop storage tank agitators Flow of liquid wastes.

FI RE PROTECTION

The plant fire protection system will consist of a foam fire extinguishing system connected to each waste and fuel storage tank, portable foam nozzles and overhead spray deflectors along the unloading dock.

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SOLIDS HANDLING

Solids handling equipment will feed empty, disposable 55 gal drums and municipal treatment plant grit and screenings to the rotary kiln. The screenings and the drums will be processed by shredding before being fed by con­veyors.

The shredded wastes will be carried by a bucket ele­vator to a belt conveyor discharging to a screw conveyor that will feed them into the rotary kiln. Grit will be de­livered separately from the treatment plant and unloaded into a storage bin. Screw conveyors will take the grit from the storage bin to a bucket elevator to be dropped onto a main conveyor belt which will feed the rotary kiln through a screw conveyor.

THERMAL REDUCTION

Investigation of available equipment to burn industrial wastes suggested the desirability of using two furnaces. One furnace to burn solid wastes and sludges, the second to burn liquid wastes (see Figs. 3 and 4 - Thermal Reduc­tion).

As designed, both furnaces are connected in parallel to a common combustion chamber where combustion will be completed and odors destroyed. Flue gases flow from the combustion chamber through an air pollution control system where acids will be neutralized and particulates re­moved. The flue gases then flow from the air pollution control system through a powerful induced draft fan and a stub-stack into the atmosphere.

FLEXIBILITY

The facility has been designed to reduce thermally, a variety of wastes from many processes - sludges and liquid wastes from industry and solid wastes and skim­mings from the wastewater treatment plant. Because in­dustrial wastes vary with each new industrial process, it must be expected that the treatment process must have the flexibility to meet industrial wastes changes in a con­tinuing new products development market.

ROTARY KILN

The rotary kiln design provides a revolving refractory­lined cylinder, slightly inclined to the horizontal, sup­ported by two riding rings resting on trunnion rolls, with the trunnion roll bearings mounted on structural steel bases.

The cylinder is rotated by means of power-driven trunnion rolls with a through shaft that extends through trunnion rolls on one side of the cylinder and is directly coupled to a helical gear speed reducer and electric motor. On either side of one of th� riding rings is an adjustable thrust roll for holding the cylinder in its longitudinal position.

Adequate draft and velocity of hot gases through the cylinder will be obtained by an induced draft fan located downstream of the air pollution control system. A dam­per located at the intake side of the fan regulates gas flow.

As designed, the cylinder is enclosed at each end by a refractory lined hood. The front hood is fitted with a supplementary burner firing into the kiln. The rear hood discharges ash through a bottom port. The firing and dis­charge hoods are fitted to the rotating kiln cylinder with angle seal rings and asbestos seal segments to prevent ex­cessive air leakage at these points.

Automatic temperature controls are used, consisting of a primary indicating.controller taking the control from the exit gases leaving the rotary chamber. When the exit gas temperature fails below a predetermined setting, the instrument increases the flow of fuel to the main burner.

A high limit control is also used taking its signal from a thermocouple in the exh?ust gases leaving the kiln. If a preset temperature is exceeded, the burners will go to low firing, the feed will stop and an alarm will sound.

The burner system is provided with its own forced­draft fan and flame protection (F . LA. approved) so that in the event of any flame or fuel failure of the pilot flame, the complete burner system will automatically shut off and sound an alarm.

The kiln is designed to burn solid wastes, spent earth, sludges, and liquid wastes. Solid wastes include disposable drums, and screenings and grit from wastewater treatment. Sludges include skimmings from the wastewater treatment plant and sludges from industry. Liquid wastes include high Btu wastes from industrial waste oil. The high Btu hydrocarbons will be fired through an air atomizing burn­er with a separate forced draft fan for supplying combus­tion air. These high Btu wastes will provide the necessary heat to maintain the kiln at a temperature sufficient to burn the other combustible wastes.

Gases from the rotary kiln will be discharged to the combustion chamber through a tangential connection. The air flow to the kiln will be controlled in part by the draft in the combustion chamber which governs the a­mount of air drawn through the seals around the peri­phery of the rotating chamber. The remaining air to the kiln will be uspplied to its high Btu burner by its forced draft fan on a basis proportional to the fuel being fired and by a fan supplying air to the inlet shroud.

326

Thermal reduction of industrial wastes involves certain factors that must have careful consideration. These fac­tors, common to most similar disposal problems, include: (1 ) permissible heat release and velocity of gases through the incinerator cylinder, and (2) adequate time of passage.

For a given capacity, there is a definite thermal heat requirement that must be satisfied. The permissible heat release, on which the sizing of this incinerator is based, is designed to combine maximum incineration efficiency with maximum equipment life and minimum maintenance. The kiln inside diameter must also take into account the velocity of gases through it; a velocity that will not create undue entrainment of fines, thereby producing an excess load on the wet scrubbing system.

To obtain complete incineration of waste and to stay within permissible limits of smoke generation requires an ample supply of air (up to 1 40 percent excess air) and exhaust operating temperatures at the rotating cylinder exit in excess of 1 200°F and normally in the range of 1 400°F to 2300°F.

The rotary kiln must function as a conveyor of material, but it must also provide a sufficient period of reten-tion to permit the material to become properly dried and pyrolysed under the chosen condition of temperature and velocity. The rotary kiln design has been so proportioned to provide this time of passage.

Spent earth and skimmings will be fed through non atomizing burners so as to be tumbled by the kiln. Screen­ings will be shredded and fed by a screw feeder. Grit will be fed from a storage bin by the same screw feeder as the screer1ings. Ash from the kiln will be discharged through a slide ga te to the ash pit.

CYCLONE FURNACE

. The cyclone furnace is a small combustion chamber where high turbulence and high temperatures are main­tained. This furnace was originally developed to burn crushed coal at heat rates of 500,000 to 900,000 Btu per cu ft per hr with gas temperatures exceeding 3000°F. Primary air, about 20 percent of the combustion air, enters tangentially through the burner. Secondary air enters the main barrel of the cyclone tangentially at very high velocities. This arrangement provides a whirling or centrifugal motion to the combustibles.

The result of this method of combustion provides com­plete burning in the cyclone chamber. The cyclone fur­nace may be operated with less than 20 percent excess air with satisfactory combustion.

The cyclone furnace will burn only high- and low-Btu liquid wastes. High Btu wastes will be fired through an air

atomizing jet burner located in the unit's sidewall. The low Btu-high water content aqueous wastes will be fired through two batteries of large diameter air atomizing burners located on opposite sides of the cyclone furnace. One battery will supply low-Btu, high water content aque­ous wastes. The other battery will supply high-Btu, low water content, acqueous wastes and/or No. 2 fuel oil. A spark-ignited lighter for firing No. 2 fuel oil will be located in the side wall opposite the high Btu burner. The high-Btu burner will maintain combustion when the low-Btu wastes cannot support combustion.

The design provides the operator with means to com­pensate for burning fuels having a wide range of Btu values, as may be directed by plant management. Excess air will be kept to a minimum, consistent with allowable furnace temperatures. Means are provided for the opera­tor to vary excess air on a proportional basis, depending on the type of fuel available. Flow of fuel will be mea-

•

sured on a volumetric basis and automatically controlled from the combustion control.

Combustion air will be supplied from a forced draft fan through a direct-fired air preheater to the windbox sur­rounding the cyclone furnace. From the wind box, the air will enter the vortex of the furnace through a damper controlled port and through two ports on each side of the unit. The air preheater provides additional heat to the furnace to dry high moisture content liquid wastes, and the air can be preheated from 80 to 400°F.

Basic control impulse will be from the combustion fur­nace temperature. Control of furnace temperature will provide a means of varying the cyclone furnace load.

The pilot flame will be automatic as defined by F . LA., namely an interrupted spark-ignited proven oil pilot. The flame scanner of the ultra-violet type is capable of proving the flame. The cyclone furnace has its own combustion safeguards that meet F . LA. requirements and local ordi­nances.

COMBUSTION CHAMBER

Gases from the kiln and cyclone furnace enter the side of the cylindrical vertical combustion chamber in a man­ner to promote mixing of gases and to encourage com­plete combustion.

The combustion chamber allows one second retention time for the gases at 2500°F. The combustion chamber has a hopper bottom to funnel ash to the ash pit. The chamber refractory is suitable to withstand higher tem­peratures should unbalanced operating conditions occur. The combustion furnace draft is used to provide a charac­terizable signal for system draft control.

327

A combustion furnace emergency stack bypasses the flue gases in case of high flue gas temperatures when de­tected at the induced draft fan inlet, or scrubber water supply failure.

HEAT RECOVERY

PLUME SUPPRESSION

Provision for partial heat recovery has been made in allowing for the future installation of a recuperator; an air to gas heat exchanger, to preheat outside air to a tem­perature of 900°F and deliver it to the induced draft fan outlet for suppression of the plume of the stack discharge gases.

Outside air suppli�d by a fan will be circulated through the recuperator and preheated to 900°F. The future re­cuperator will be located between the combustion cham­ber discharge and the air pollution control intake.

STEAM GENERATION

Heat recovery to generate steam is not being incorp­orated at this time.

POLLUTION CONTROL SYSTEM

An advanced air pollution control system has been incorporated into the design of the facility. It was deemed necessary to optimize the air pollution control system to the utmost of present day capability because the noxious gases and particulates vary continuously.

QUENCHING-SPRAY AND VENTURI SCRUBBER

Flue gases leaving the combustion furnace will be cooled in a spray chamber by quench sprays to a range of 1 400 to 1 000°F before entering the high-energy variable throat venturi scrubber where most of the particulate mat­ter will be removed from the flue gases.

A slurry of fly ash, sodium carbonate, and reaction products will be recirculated through the venturi. Part of this slurry will be used as wall wash to present a wetted wall to the incoming flue gases. The remaining slurry will be introduced at the venturi throat through a series of spray nozzles.

Particulate removal, as well as an initial stage of S02 removal, is accomplished in the venturi scrubber. The venturi throat area can be varied, actuated by a differen­tial pressure signal measured across the venturi.

ABSORBER-DEMISTER

Flue gases from the venturi will pass up through a two­stage absorber where the sodium carbonate slurry will

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come into intimate contact with the gas and remove sul-phur dioxide and hydrochloric acid, forming sodium sul­fite or sulfate, and sodium chloride_

Scrubbed flue gases will continue to flow upward from the absorber to a moisture separator (demister) for re­moval of water droplets_ The demister will have a wash system that may be used to periodically wash salts from the elements. The gases will be drawn from the demister by an induced draft fan and discharged to the atmosphere through a stack.

RECIRCULATION TANK AND PUMPS

A recirculation tank will be located directly below the venturi-absorber to collect the recirculation slurry and per­mit adequate retention time at full load. The tank is divided through the center by a baffle plate that separates the absorber and venturi recirculation tanks . .

Fresh slurry will be added to the absorber recirculation tank to permit maximum usage of the fresh chemical to promote sulphur dioxide removal. Spent slurry from the absorber will flow from the absorber recirculation tank to the venturi recirculation tank where a controlled amount

will be removed from the system as blowdown. Horizontal centrifugal pumps, with replaceable butyl

liners and butyl molded impellers (steel core) will recircu­late the slurry.

RESIDUE DISPOSAL

An ash sluicing system will remove ash from the kiln and the bottom of the combustion chamber. At the op­tion of the operator, a pneumatically operated slide gate on the discharge of the kiln will isolate the kiln from the hopper. The combustion chamber will be open for con­tinuous ash discharge to the hopper. The ash pit will con­tain a baffle plate to separate the two ash inlets.

During normal operation the ash discharge from both sources to the ash pit will be continuous. The ash pit will

, .

be fIlled with water above the bottom of the baffle plate to prevent circulation of gases through the hopper. During the time ash is being pumped from the pit, the gate on the kiln will be closed and the water level can be lowered below the baffle plate.

Operation of the ash system may be controlled either from the combustion control panel or locally. The opera­tor will start the system and it will go through the sequence of starting the the booster pump, the jet-pulsion pump, and the sluicing nozzles. Gates on the kiln and ash pit will be

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THERMAL REDUCTION SIDE ELEVATION

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328

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. positioned to prevent gas circulation and to allow dis-charge of ash from the pit.

The residue will be sluiced to an adjoining lagoon that also also receives the residue from four multiple hearth fur­naces.

OPERATION

The thermal oxidation facility will operate 24 hours a day, 5 days per week, with a shutdown on weekends.

The rotary kiln and cyclone furnace will operate in parallel with exhaust gases discharging into the combus­tion chamber. The exhaust gases then pass through a quenching chamber, a venturi scrubber, and an induced­draft fan to a refractory fired steel stack for discharge to the atmosphere.

The facility has been designed to operate under the following conditions of continuous operation:

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CONYEYOR

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329

(Btu/hr. x 10·) Furnace Load Continuous Max. (2 hr)

Rotary kiln

Cyclone Furnace

Total

Gas Temperatures (0 F):

Rotary kiln - out

Cyclone Furnace - out

Combustion Chamber - out

Quenching - out

Scrubber - out

Recuperator - in

Air Temperatures (OF):

Rotary kiln - in

Cyclone Furnace - in

Recuperator - out

Quencher

Scrubber

Gas Absorber

Blowdown

ROTARY KILN

Water Flow (qpm)

55 65 59 77

114 142

1600-2400 2000-3100 2000-2800 1000-1400

180 2100

80 80- 400

900

80 1700 3600

200

Solid wastes - disposable drums and screenings - will be preprocessed by shredding before feeding into the fur­nace. Solid waste handling will be by automatically­operated conveyors from the truck unloading, shredding, and feeding system.

Treatment plant skimmings will by pumped from the plant into storage tanks for concentration of the mixture by water removal. The skimmings then will be macerated and pumped into the furnace at a rate programmed by the operator.

The rotary kiln also will be fed industrial wastes with a high-water content. Air atomized burners fed with high Btu waste and/or No. 2 fuel oil will provide the necessary heat to main tain adequate kiln temperatures. The kiln will be partially sealed and the combustion air will be provided by a forced-draft fan. The high-Btu waste burner will be used to preheat the kiln prior to startup in addition to maintaining kiln temperature.

CYCLONE FURNACE

The combustion chamber temperature of the cyclone furnace will be maintained and controlled automatically. Liquid wastes for the cyclone furnace will be supplied from 8-hr batch tanks. The batch blending tank will be prepared in advance by blending a variety of wastes scheduled for burning during a designated 8-hr shift. The batch-blend storage tank will provide the cyclone furnace with a uniform blend of waste fuel, whose characteristics will be made known to the operator by the laboratory.

AIR POLLUTION CONTROL SYSTE M

As described above, the hot gases will be cooled in a quench spray chamber and then passed through the high­energy venturi scrubber for particulate removal. Predeter­mined differential pressure across the venturi scrubber will be controlled automatically for high efficiency particulate removal.

Flue gases leaving the high energy venturi scrubber enter the gas absorber and demister for absorption of noxiou.s pollutant gases and collection of water mist as described previously. The primary function of the tray gas absorber is to serve as a direct contact type to absorb condensable gases. The secondary function is to remove a major percentage of particulates remaining in the gases leaving the scrubber. Sodium hydroxide will be used to neutralize noxious gases and the salts resulting from action in the absorber/demister will be removed by blowdown.

CONTROLS AND INSTRUMENTATION

The combustion control system will provide a system capable of burning a variety of liquid wastes efficiently, without resulting odors.

Excess air will be kept to a minimum consistent with allowable furnace temperatures. Means are provided for the operator to vary excess air on a proportional, not bias, basis. However, means are available for operator adjust­ment of excess air in case of high furnace temperatures resulting from the burning of very high Btu waste fuels. Proper conditions for startup of burners have been estab­lished to provide maximum safety precautions.

Instrumentation has been provided to monitor drafts, pressures, temperatures, oxygen in flue gasses, and pollu­tants.

330

Power failure safety precautions have been incorporated to shut down the system in an orderly sequence.

Rising temperatures in the induced draft fan inlet would shut down the system in an orderly sequence.

Rising temperatures in the induced draft fan inlet would shut down the facility, and open the emergency stack without recycling, before the cause of failure could be investigated and resolved.

LABORATORY TESTING

Because of the extreme variability in the character and content of the wastes that will be received at the treat­ment plant, each delivery must be tested to determine its constituents and determine to which storage tank it is to be dischargec. Such testing procedures will also determine whether or not the waste is acceptable for treatment and disposal.

Obviously, the larger the size of the tank, truck, or con­tainer in which delivery is made, the less the time per unit volume that will be required for testing. This testing-time factor will be an important part of the charge schedule for treating the waste. Results of the tests will be recorded and may be included on the statement of billing charges.

The laboratory will have facilities to run proximate analysis tests of every waste supplied to the facility for thermal oxidation.

Such tests will include the determination of

Moisture Volatile matter Fixed carbon Ash Heating valve Flash point Specific weight Viscosity Ash fusion temp. pH

Percent by weight Percent by weight Percent by weight Percent by weight Btu per lb dry OF Ib/gal SSU - Say bolt Universal OF Unit

The laboratory will have each batch tank waste analyzed and a copy of the test results will be given the operator before the batch is placed into the operating sequences.

Certain wastes such as skimmings and spent earth, are expected to be fairly consistent. They will not have to be analyzed continuously, but will be analyzed periodically to determine any changes.